The field of art to which this invention pertains is homopolymers and copolymers of vinylphenol
Homopolymers and copolymers of 4-hydroxystyrene, or p-vinylphenol as it is also called, are known compositions which have been used, for example, in the manufacture of metal treatment compositions, photoresists, epoxy resins and epoxy resin curing agents. Polymers of p-vinylphenol can be made by polymerizing p-vinylphenol itself. However, p-vinylphenol is an unstable compound and must be refrigerated to prevent it from polymerizing spontaneously. Even under refrigeration, the monomer will slowly polymerize to low molecular weight polymers. 4-Acetoxystyrene, the acetic acid ester of p-vinylphenol, is a stable monomer which can be readily homopolymerized and copolymerized to low, medium and high molecular weight polymers. After polymerization, the phenolic ester group can be hydrolyzed to produced p-vinylphenol polymers.
Corson et. al., Journal of Organic Chemistry, 23, 544-549 (1958), describe a 5 step process for making p-vinylphenol from phenol. The phenol is first acetylated to p-hydroxyacetophenone which is then acetylated to p-acetoxyacetophenone. This compound is hydrogenated to p-acetoxyphenylmethyl carbinol which is then dehydrated to p-acetoxystyrene. The p-acetoxystyrene is saponified to p-vinylphenol using potassium hydroxide.
The ester interchange reaction of poly 4-acetoxystyrene in methanol using sodium methylate is described in U.S. Pat. No. 2,276,138. About 84 percent of the acetate groups are removed by the interchange reaction. Packham, in the Journal of the Chemical Society, 1964, 2617-2624, describes the hydrolysis of crosslinked poly-4-hydroxystyrene by refluxing the polymer in alkaline aqueous dioxane for 2 days. In U.S. Pat. No. 4,544,704, a copolymer of sytrene and p-isopropenylphenylacetate is hydrolyzed with aqueous sodium hydroxide in methanol and tuluene using a small amount of benzyltrimethylammonium chloride as a phase transfer agent. Arshady et. al., Journal of Polymer Science 12, 2017-2025 (1974), hydrolyzed copolymers of styrene and acetoxystyrene to the vinylphenol polymer using hydrazine hydrate in dioxane.
the hydrolysis or methanolysis of polymers of 4-acetoxystyrene is very difficult to carry to 85 percent or above completion. Also, when alkali metal hydroxides are used, it is extremely difficult to remove all traces of alkali metal salts which can be detrimental for some applications and uses of the vinylphenol polymer.